Structural, magnetic and transport properties of carbon chains sandwiched between zigzag graphene nanoribbons

Abstract

We investigate the structural, magnetic properties and spin polarized transport of monatomic carbon chains covalently interconnected between zigzag graphene nanoribbon (ZGNR) leads with first-principles and non-equilibrium Green's function methods. It is revealed that an even numbered carbon chain is nonmagnetic when connected at the center of the armchair side of ZGNRs, but it becomes spin polarized and a net magnetic moment (about 0.1 μ_B) is developed when it moves to the edge. In contrast, an odd-numbered carbon chain is magnetic when it lies at the center of the armchair side and the magnetic moment decreases when the carbon chain moves to the edge. The total magnetic moment of the ZGNR/C_n/ZGNR junction depends on the magnetic alignment between two zigzag edges. Compared with that of ZGNR/C₉/ZGNR with C₉ chain anchoring at the center, the magnetic moment of the junction increases by 2.2 μ_B in the antiferromagnetic configuration and decreases by 1.5 μ_B in the ferromagnetic alignment when the carbon chains migrate from the center to one edge. Thus, the ZGNR/C_n/ZGNR junctions show rich magnetic varieties by modulating the carbon chain anchoring sites and the zigzag edge magnetic coupling. Further, spin-dependent transport calculations indicate that the ZGNR/C₉/ZGNR junction behaves as a perfect spin-filter in spintronic circuits.